This invention relates generally to magnetic disk drives, more particularly to magnetoresistive (MR) read heads, and most particularly to methods and structures for current-perpendicular-to-plane operation of submicron MR heads.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1A and 1B, a magnetic disk drive 10 of the prior art includes a sealed enclosure 12, a disk drive motor 14, a magnetic disk 16, supported for rotation by a drive spindle S1 of motor 14, an actuator 18 and an arm 20 attached to an actuator spindle S2 of actuator 18. A suspension 22 is coupled at one end to the arm 20, and at its other end to a read/write head or transducer 24. The transducer 24 typically includes an inductive write element with a sensor read element (shown in FIG. 1C). As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the transducer 24 causing it to lift slightly off of the surface of the magnetic disk 16, or, as it is termed in the art, to "fly" above the magnetic disk 16. Various magnetic "tracks" of information can be read from the magnetic disk 16 as the actuator 18 causes the transducer 24 to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk drives is well known to those skilled in the art.
FIG. 1C depicts a magnetic read/write head 30 including a read element 32 and a write element 34. The edges of the read element 32 and write element 34 also define an air bearing surface, ABS, which faces the surface of the magnetic disk 16.
Read element 32 includes a first shield 36, a second shield 38, and a read sensor 40 located between the first shield 36 and the second shield 38. One type of read sensor 40 is a magnetoresistive (MR) sensor which can be a variety of types, such as anisotropic magnetoresistive (AMR), spin valve, and giant magneto-resistive (GMR). The particular read sensor 40 shown is a multilayer GMR, formed of successive layer pairs 42 of various materials. Such an MR device typically can be formed by depositing the layer pairs 42 one upon the next to form a multilayer wafer (not shown). The material of each layer and the ordering of layers are appropriately selected to achieve a desired read performance. Multiple portions of the wafer are then removed to provide multiple read sensors 40.
The operation of the read element 32 can be better understood with reference to the perspective view of read element 34 in FIG. 1D. A sense current I is caused to flow through the read sensor. While here the sense current is shown injected through the shields, other configurations have the read sensor electrically isolated from the shields, with additional leads injecting the sense current I. As the sense current passes through, the read sensor exhibits a resistive response, which results in a particular output voltage. The higher the output voltage, the greater the precision and sensitivity of the read sensor in sensing magnetic fields from the magnetic medium 16.
The output voltage is affected by various characteristics of the read element 32. For example, the greater the component of the sense current I that flows across the read sensor layers, the greater the output voltage. This component of the sense current I is called the current-perpendicular-to-plane component, CPP. On the other hand, the component of the sense current I that flows along the read sensor layers 42 is the current-in-plane, CIP, which results in lower output voltage. In the configuration of FIG. 1D, the first and second shields 36, 38 are conductive and are in electrical contact with the read sensor 40. Here, the sense current I of the read sensor 40 flows, for example, from the first shield 36 to the second shield 38 through the read sensor 40. As the sense current I flows through the read sensor 40, the current flows substantially perpendicularly to the orientation of the layers 42 of the read sensor 40. Thus, substantially all of the sense current I is CPP. Other read sensors may be designed to operate with varying CPP and CIP components of the sense current. However, it is desirable to maximize the CPP component to maximize the output voltage of the read sensor. The design and manufacture of magnetoresistive heads, such as read sensor 40, are well known to those skilled in the art.
Write element 34 is typically an inductive write element and includes a first yoke element 44 and the second shield 38, which forms a second yoke element, defining a write gap 46 therebetween. The first yoke element 44 and second yoke element 38 are configured and arranged relative to each other such that the write gap 46 has a particular throat height, TH. Also included in write element 34, is a conductive coil 48 that is positioned within a dielectric medium 50. As is well known to those skilled in the art, these elements operate to magnetically write data on a magnetic medium such as a magnetic disk 16.
Although current MR read sensors such as read sensor 40 have been used in the past, their performance is limited. In particular, their output voltage is limited by various factors such as cross-sectional area that is normal to the sense current vector (i.e., decreasing output voltage with increasing area), and the device length that is parallel to the sense current vector (i.e., decreasing output voltage with decreasing length). With demand for increasingly smaller read/write heads, the shield-to-shield height H between the read element first and second shields 38, 44 is increasingly smaller, thus leaving increasingly less space to accommodate the read sensor 46. Thus, in a read sensor such as shown in FIG. 1D, decreasing height H results in decreasing device length, thereby reducing the sensor output voltage. Furthermore, even without limitations on device length, GMR multilayer properties have been found to degrade as the number of multilayers (i.e., layer pairs) increases. In particular, degradation has occurred above 20-30 multilayers.
In addition to the limitations of currently available materials, edges E (shown in FIG. 1D) of each layer in a multilayer device can be damaged in the fabrication process. For example, during a cutting operation to remove a single read sensor from a wafer, materials from individual layers may be smeared along the layer edges. Thus, the sense current I traveling perpendicular to the layers may be shunted at the edges, thereby reducing the effectiveness of the sense current I to drive the MR read sensor.
Also, the fabrication of read sensors is becoming increasingly more complex and expensive as increasingly smaller MR read/write devices are sought by users. Particularly, designs are being driven to submicron geometry scales. Such geometries are typically formed by direct photolithographic techniques which are more time and cost consuming. In addition to the challenges of the device size itself, fabrication tolerances are accordingly becoming increasingly smaller.
Thus, what is desired is an MR head, and method for making the same, that has increased performance, while limiting cost and complexity, even at increasingly smaller MR head sizes.